The present;invention relates to the field of angioplasty. In particular, the present invention relates to an intravascular catheter, such as a dilatation balloon catheter, of the type which is advanced over a guide wire and which has a short guide wire lumen adjacent the distal end of the catheter.
Angioplasty procedures have gained wide acceptance in recent years as an efficient and effective methods for treating certain types of vascular diseases. In particular, angioplasty is widely used for stenoses in the coronary arteries, although it is also used for the treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation balloon catheter to treat a stenosis and thereby reestablish an acceptable blood flow through the artery. The dilatation catheter includes an elongated tubular shaft and an inflatable balloon carried at a distal end of the shaft. In operation, the catheter is inserted through a hollow guide catheter which has been previously introduced into a patient's vascular system from a location remote from the heart (e.g., femoral artery). The proximal end of the guide catheter remains outside the patient while the distal end of the guide catheter is positioned at the coronary artery ostium. A dilatation catheter is introduced into the proximal end of the guiding catheter and advanced to the distal end of the guide catheter. Then, by using fluoroscopy, the physician guides the dilatation catheter the remaining distance through the vascular system until the balloon is positioned across the stenosis therein. The balloon is then inflated by supplying fluid under pressure, through an inflation lumen in the catheter, to the balloon. The inflation of the balloon causes a widening of the lumen of the artery to reestablish acceptable blood flow through the artery. After a short inflation period (e.g., 30-90 seconds), the balloon is deflated and the arterial treatment evaluated to determine whether the procedure has reestablished an acceptable blood flow. The evaluation is conducted by introducing a radiopaque dye solution into the artery via the guiding catheter, and then observing the dye flow using fluoroscopy. If necessary, the dilatation procedure is repeated with the catheter balloon being re-inflated. In procedures in the peripheral vessels (vessels other than coronary vessels), a guide catheter may not always be used.
The placement of the dilatation balloon across a stenosis in a coronary artery can be a difficult procedure. Movement of the elongated dilatation balloon catheter (e.g., 135 cm) is achieved by manual manipulation of its proximal end outside the patient. The ability of a catheter to bend and advance through the vasculature is commonly referred to as the "trackability" of the catheter. "Pushability" refers to the ability of the catheter to transmit the longitudinal forces applied by the physician along the catheter shaft to advance the distal end of the catheter through a coronary artery to and across the stenosis. Preferably, a catheter has a low profile, and is relatively trackable and pushable.
One common type of dilatation catheter has a separate guide wire lumen in the catheter so that a guide wire can be used to establish the path through the stenosis. The dilatation catheter can then be advanced over the guide wire until the balloon on the catheter is positioned within the stenosis.
During an angioplasty procedure, it is sometimes desirable to replace an existing catheter with another catheter. In that instance, the physician prefers to maintain the position of the guide wire in the patient's vascular system relative to the stenosis as the catheter is withdrawn over the guide wire. In the event of an abrupt closure of a partially dilated lesion when the balloon catheter has been withdrawn after an initial dilatation, the wire will maintain the path through the lesion. Any significant or uncontrolled movement of the exposed guide wire is avoided, so that the guide wire does not become dislodged from its position across the lesion. In order to exchange a catheter with a guide wire lumen that extends the entire length of the catheter shaft, a longer exchange wire is sometimes exchanged for the standard guide wire, or a guide wire extension may be provided. The use of long exchange wires or guide wire extensions present a great length of guide wire outside the patient which must then be managed during the catheter exchange procedure. This not only proves awkward but typically requires two persons.
In one type of dilatation catheter, the guide wire lumen extends from a distal end of the catheter through the dilatation balloon and then exits the catheter at a point proximal of the balloon. To accomplish a catheter exchange using a catheter having a distal guide wire lumen, the initial catheter can be preloaded onto the guide wire before the guide wire is inserted into the guide catheter, or positioned on the proximal end of the guide wire once the guide wire has been introduced into the guide catheter. In either case, the guide wire is steered through the guide catheter, coronary vessel and across the stenosis. Then the proximal exposed portion of the guide wire (outside the patient) is grasped and the catheter is pushed distally to advance it along the guide wire and across the stenosis.
If a different dilatation balloon is then desired, the catheter is withdrawn without removing the guide wire from across the stenosis. First, the guide wire is grasped near the proximal end of the guide catheter. The catheter is then withdrawn, and when the proximal opening of the guide wire lumen is reached, the grasping hand is moved incrementally away from the proximal opening of the guide wire lumen on the catheter. The catheter is then incrementally withdrawn until the catheter is fully removed from the guide catheter and the guide wire is thus again exposed and accessible adjacent to the proximal end of the guide catheter. Once the initial catheter has been completely removed from the guide wire, a second catheter is loaded onto the guide wire by inserting the proximal end of the guide wire into a distal opening of the guide wire lumen in the second catheter. This second catheter is then advanced by "feeding" the catheter distally over the guide wire while holding the guide wire stationary. The proximal end of the guide wire will then emerge out of the proximal opening of the distal guide wire lumen and is accessible again for gripping by the physician. By now holding onto the exposed portion of the guide wire in this manner, the second catheter can then be advanced distally along the stationary guide wire to a desired position in the patient's vasculature.
Another type of catheter places the entire guide wire lumen adjacent the distal tip of the catheter (distally of the intravascular interoperative element (e.g., dilatation balloon) on the catheter). In a catheter design where the guide wire does not extend through the catheter balloon, it is important that the catheter structure provide sufficient rigidity along the catheter shaft and through the balloon (all the way to the distal tip of the catheter where the guide wire lumen is located), so that the catheter has the necessary pushability.